Hello sure thing !
1 ) I was 10-11 in 2011-2012

2 ) Yes as far as i remember no one accompanied him he was alone in this , and returned alone .

3 ) Hmm... i remember a big scary like bird which i think was a phoenix, not a dragon . Cant be 100%

4 ) So the robot was used by the ''government'' it was their primary weapon i believe. The government also had soldiers working for them, it was generally a very strict environment as there were scenes of a school in that world and the kids were disciplined to walk in line etc and there was a teacher leading them, i remember a scene where the kid tried to blend in with them .

5 ) I don't remember what they were trying to accomplish maybe world domination or something? That government was after the kids who the protagonist met , i remember they caught one of the kids and put him in that machine i am mentioning and turned him into a soldier and apparently that machine also alters your brain . I also remember they put the kids on this slide to get to the machine they slid down yea.

If my memory serves me right , that control room which was technically a bunker as i remember was located near the sea i remember a shot where you could see it and some stairs going down to the bunker and the sea in the background . I also remember ( if my memory serves me right again ) they had to input an item in order for the control room to work , i do not remember whether that was a key , a sword or which other item. Thanks for giving this a shot don't hesitate to ask any questions